SPOT COLOR SUBSTITUTION FOR DIGITAL WATERMARKING

• US 20160198064A1
• Filed: 11/04/2015
• Published: 07/07/2016
• Est. Priority Date: 08/12/2014
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Bai, Yang, Falkenstern, Kristyn R., Reed, Alastair M.
• Granted Patent: US 9,667,829 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
• CPC Class Codes: H04N 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• CPC Class Codes: H04N 1/32251 in multilevel data, e.g. greyscale or continuous tone data
• CPC Class Codes: H04N 1/32267 combined with processing of the image
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 1/54 Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6008 with primary colour signals, e.g. RGB or CMY(K)
• CPC Class Codes: H04N 1/6013 by simulating several colour corrected versions of the same image simultaneously on the same picture reproducer
• CPC Class Codes: H04N 1/622 with simulation on a subsidiary picture reproducer
• CPC Class Codes: H04N 1/628 Memory colours, e.g. skin or sky

Abstract

The present disclosure relates generally to digital watermarking for spot colors. In one implementation a substitute spot color+CMY tint is selected to replace an original spot color. The CMY tint can be transformed to carry a digital watermark signal. Of course, other features, combinations and technology are described herein.

Claims

1. A digital watermark embedding method comprising:

obtaining data associated with a spot color S_a, the spot color S_a comprising a component of a color design;

using one or more configured processors, determining a screen S_s of the spot color S_a;

selecting a substitute spot color candidate S_b1 by;

i) evaluating color distance or color error between the substitute spot color candidate S_b1 and the screen S_s, and ii) evaluating brightness of the substitute spot color candidate S_b1 and the screen S_s;

using one or more configured processors, determining a Cyan (C), Magenta (M) and Yellow (Y) process color tint that when combined with the substitute spot color candidate S_b1 approximates the spot color S_a;

transforming a determined CMY process color tint with a digital watermark signal to embed the digital watermark signal in the CMY process color tint, said transforming yielding a watermarked CMY process color tint; and

combining the watermarked CMY process color tint and the substitute spot color candidate S_b1, said combining yielding a digital watermarked substitute spot color.

2. The method of claim 1 in which said selecting a substitute spot color candidate S_b1 further evaluates the brightness of the spot color S_a.

3. The method of claim 1 in which said determining a CMY process color tint determines by minimizing color error or color distance between i) a combination of a CMY color tint and the substitute spot color candidate S_b1, and ii) the spot color S_a, in which the substitute spot color candidate S_b1 and the spot color S_a remain constant during the minimization.

4. The method of claim 1 in which said selecting selects a plurality of substitute spot color candidates S_bi, where i is a positive integer.

5. The method of claim 4 further comprising:

using one or more configured processors, determining a plurality of CMY process color tints that when combined respectively with their substitute spot color candidate S_bi each approximates the spot color S_a.

6. The method of claim 1 further comprising substituting the digital watermarked substitute spot color for the spot color S_a within the color design, said substituting yielding a transformed color design.

7. The method of claim 6 further comprising printing the transformed color design on a physical substrate.

8. A printed product package including the physical substrate, in which the physical substrates including the transformed color design printed by the method of claim 7.

9. The method of claim 1 in which the CMY tint comprise a Black (K) process color component, and said determining a CMY process color tint comprises determining a CMYK process color tint.

10. The method of claim 1 in which said determining a screen S_s of the spot color S_a determines the screen S_s with consideration of the screen S_s being combined with a Cyan (C), Magenta (M) and Yellow (Y) process color tint

11. A digital watermark embedding system comprising:

an input to receive color data;

memory comprising data associated with a spot color S_a, the spot color S_a comprising a component of a color design;

one or more processors configured for;

generating a screen S_s of the spot color S_a;

means for evaluating substitute spot color candidates to select a substitute spot color candidate S_b1 including;

i) means for evaluating color distance or color error between the substitute spot color candidate S_b1 and the screen S_s, and ii) means for evaluating brightness of the substitute spot color candidate S_b1 and the screen S_s;

in which said one or more processors are configured for;

determining a CMY process color tint that when combined with the substitute spot color candidate S_b1 approximates the spot color S_a;

means for embedding a digital watermark signal in the CMY process color tint, said means for embedding producing a digital watermarked CMY process color tint; and

in which said one or more processors are configured for;

merging the watermarked CMY process color tint and the substitute spot color candidate S_b1, the merging yielding a digital watermarked substitute spot color.

12. The system of claim 11 in which said means for evaluating substitute spot color candidates comprises means for evaluating the brightness of the spot color S_a.

13. The system of claim 11 in which the determining a CMY process color tint determines through minimizing color error or color distance between i) a combination of a CMY color tint and the substitute spot color candidate S_b1, and ii) the spot color S_a, in which the substitute spot color candidate S_b1 and the spot color S_a remain constant during the minimization.

14. The system of claim 11 in which said means for evaluating substitute spot color candidates selects a plurality of substitute spot color candidates S_bi, where i is a positive integer, and said one or more processors are configured for:

determining a plurality of CMY process color tints that when combined respectively with their substitute spot color candidate S_bi each approximates the spot color S_a.

15. The system of claim 11 in which said one or more processors are configured for substituting the digital watermarked substitute spot color for the spot color S_a within the color design, said substituting yielding a transformed color design.

16. A digital watermark embedding method comprising:

obtaining data associated with a first spot color S_a, the first spot color S_a comprising a component of a color design;

determining a plurality of substitute spot color candidates S_b1-S_bi, where i is an integer, by evaluating—

for each substitute spot color candidate—

color distance metrics between data associated with the substitute candidate spot color and the data associated with the first spot color S_a;

determining a Cyan (C), Magenta (M) and Yellow (Y) tint for each of the plurality of substitute spot color candidates S_b1-S_bi;

using one or more electronic processors, simulating an overprint of each of the plurality of substitute spot color candidates S_b1-S_bi with its respective CMY tint, and for each of the overprinted substitute spot color candidates, generating an Lab or Chroma distance metric relative to the first spot color S_a;

based on generated distance metrics, determining final spot color candidates;

for at least one of the final spot color candidates, and using one or more electronic processors, transforming its respective CMY tint with a digital watermark signal; and

substituting the at least one of the final spot color candidates plus its transformed CMY tint for the first spot color S_a in the color design.

17. The method of claim 16 in which the data associated with the substitute candidate spot color comprises lab data.

18. The method of claim 16 in which the data associated with the substitute candidate spot color comprises RGB or CMYK data.

19. The method of claim 16 in which said determining final spot color candidates comprises determining Lab distance values or Chroma distance values relative to the first spot color for each of the plurality of substitute spot color candidates.

20. The method of claim 16 in which said determining final spot color candidates comprises determining Lab distance values and Chroma distance values relative to the first spot color for each of the plurality of substitute spot color candidates.